Fitbit Step Accuracy & Using Apple Watch with Fitbit

Choosing the right wellness tracker can be hard. There are a number of top devices on the market these days, and they can cost a pretty penny. At any given time FitBit themselves will be selling 4-5 different “Trackers” and that is independent of the SmartWatches that it makes.  Part of choosing the right device for you will come down to the app experience that they pair it with, and the styles which are made available.

But you should not take for granted how accurate each device is. If you are looking to stay motivated to take the most steps, you will want a tracker that is very accurate in how it tracks step count. Care more about monitoring your heart rate, then it will be necessary to ensure that the heart rate sensor on your device is most accurate. Don’t care about the detail overall? That’s fine, many devices can be inaccurate to some controlled lab setting, but still offer a good enough approximation, one that helps you get up off the couch everyday and get moving. 


fitbit dashboard showing step count using apple watch

Fitbit is one of the most popular. But how accurate is the Fitbit step tracker compared to others? For the most part Fitbit step accuracy is good, the steps taken on it match that of Apple Watch within a few percent. This is much better than the Amazon Halo step tracker which seems to overestimate steps by up to 20%. To be fair in none of these have we tested against a physical count of steps over the entire day. 

On short runs and walks we have individually counted up to 1000k steps and in that case the Fitbit was almost spot on, as was the Apple Watch, with both being within 1% accuracy of what was counted. Even so this is not a great estimate as you would expect the accuracy to be best when walking. The bigger concern is seeing when the wrist worn devices count a step when you are not moving. This is the hypothesis of the Amazon Halo, that some random movement of the wrist is trigger extra steps when none are taken. 

This anecdote matches what was found in peer reviewed journals, which found the Fitbit to be accurate within 3% in lab settings and 10% when in real world settings. 

So Why Is Fitbit Not Accurate?

When it comes to step counting, the accuracy is based on the how easy it is to determine when a step was taken. Inside the wrist worn device is an accelerometer , a tiny sensor that measures how quickly you are accelerating in various directions.

When worn on a wrist, this means the device can create a signal as you swing your arm back and forth while walking. Even holding your hand relatively steady, say while carrying books or a drink, the bounce of your step is fairly easy to see in the accelerometer data.

Still, there is no perfect way to measure this signal. Many other activities can look similar, in a data sense, to that of taking a step. Likewise taking a step while doing something else with your hands may not always look the same and it will be hard for the device to count that step. Given the amount of steps that you take in a day, it is not surprising that some of these will be overlooked or smoothed out by the signal, and therefore not counted. 

Even given the accuracy issues, it is somewhat irrelevant if your FitBit gets exactly the right number. That is because there is no magic thing that happens in your body once you take your 10,001 step for the day. It’s not like taking enough steps in a day is a binary thing, you can vary the amount of steps and activity you do and still achieve the goal of staying active overall. This is why it is important to remember, even if your watch tracker is not accurate, if it motivates you to stay fit and active then it is doing its job.


Which Fitbit Is Most Accurate?

Not all Fitbit activity trackers are created equal. There are two major captives of the popular wrist worn devices, the watches and the pure trackers.

Watches serve the additional uses of providing a watch and app access on your wrist. This means less battery life overall, but also more compute power. That said, for the most part the technology used to monitor steps is the same. The sensor inside, the accelerometer, is the piece that generates the signal for how much movement has been created. There is some indication that Fitbit varies the sensor in each of there devices, at the very least updating them in new generations. That means that you are likely to get a more advanced, and more accurate, sensor in a newer model Fitbit Charge 5 vs Fitbit Charge 4, and the same goes for a Fitbit Sense or Fitbit Versa 3 Watch vs Fitbit Versa 2.